Methane is a well-known greenhouse gas and inventory of its sources is currently a priority task of the scientific community as well as of industrial big role players. Release rates of CH4 are mandatorily reported in Europe by most of the industrial facilities like coal mines. However, bottom up inventories are still very heterogenic. In case of Silesia area yearly methane release estimates range from 350 Tg/year (reported by national inventories in Poland and Ukraine) over 500Tg/year (EPRTR database) and up to 1300Tg/year (as reported by EDGAR database). All these numbers are elaborated in a specific way and may be used by policy makers for important decisions concerning greenhouse gas limitations and reduction.

In this situation, independent measurements are required to verify the reported emission rates and monitor the CH4 concentration in the atmosphere. Certainly, measurements performed “on ground” can’t validate the emission rate from particular exhaust mine shafts but may be treated as the preliminary indicator of big sources. The advantage of airborne platforms in this case is evident and FOAM-Silesia campaign aimed at quantifying the methane burden over Silesia area with direct measurements of methane plumes from mining facilities.

FOAM Silesia was initially designed to cooperate with another aircraft campaign – COMET. However, due to the change of the COMET timeframe, FOAM was finally designed as a precursor campaign of COMET, aimed to perform airborne measurements in 2018 over the same area. A group of scientists from Poland (AGH) and Germany (FUB, UBremen) (see photo 1) undertook a joint effort to proceed with the delayed flight campaign using a smaller Cessna aircraft. The first direct airborne in-situ measurements of methane were performed by the FUB Cessna aircraft on 21 September 2017 in Germany over the landfill Schoneiche and on 29 September in Poland over Silesia. Regarding the measurements over Silesia, the aircraft was deployed at the Katowice – Pyrzowice airport and reported an anomaly high methane concentration already at the runaway of the airport. The main goal of the different measurement missions was divided into 4 categories:

Mining exhaust shafts (3 days of successful flights)

City gas network leakages (measurements over the city area was cancelled during the campaign due to very low signal and CTR restrictions)

Landfills (moved to German landfill Schoneiche )

Natural wetlands (emission not visible by aircraft instrumentation due to highly elevated methane concentration over Silesia area connected with mining industry)

Unfortunately, a large part of the Silesian area is covered by temporal flight restriction areas (TRAs) and airport controlled traffic regions (CTRs) . Only westerly winds can assure proper methane mass-balance measurements using wall patterns performed by the aircraft in the south-eastern part of the region. During the measurements, the Moravian Gate, however, induced southerly winds over the territory of South Silesia where most of the methane is released from mines. Therefore during the first days of the campaign, only parts of the relevant areas could be properly covered (photo 3). The Aero club in Rybnik did not support the FOAM flight due to the heavy traffic in the airfield and access to the Rybnik TRA was possible only on one day. Also a parachute school controlling one of the TRAs was located there preventing lower flights. Atmospheric conditions during the flight appeared to be principally variable and wind direction changed spontaneously from SW to SE directions in the time-scale of an hour. In this case, wind forecasts were not reliable during campaign.

Successful flights were performed on 29 September, and 1 and 2 October 2017. A successful short preparation flight was performed also on 21 September over a managed German landfill to asses if the sensitivities of the in-situ instrumentation are sufficient to also detect lower emissions from well controlled landfills. Data collected during the flights are currently used to compare modelled values with measurements which could lead to validation of applied inventories. Due to inappropriate weather conditions and the location of most of the landfills within the restricted TRAs and CTAs, it was decided to perform an additional full measurement flight over the landfill Schöneiche near the home Airport of the Cessna. This allowed the team to perform measurements during more appropriate weather conditions, as landfill measurements require calm to moderate winds and a dedicated flight pattern near the source due to the much weaker methane emissions than the coal mines.

Photo 3: Map of planned flight on 2 October with important waypoints, also showing the different TRAs and CTAs inside the measurement area

Photo 4: Preliminary results obtained from the Picarro CRDS analyser installed on board of the FUB Cessna from 29.09.2017 (red colour indicates elevated methane concentration). Flown was a search pattern at lowest altitude downwind of the Pniowek mine for searching of plume positions inside the Rybnik TRA. In addition also two “walls” in downwind direction from Pniowek were flown for flux inversion.